fMRI, Genes and Outcome for Cochlear Implants in Infants

Cochlear implantation (CI) has revolutionized the management of congenitally deaf children (Waltzman and Cohen 1998). A growing body of evidence suggests that that performing CI as early as possible in congenitally deaf infants and toddlers results in the best outcome (Govaerts, De Beukelaer et al. 2002; Hammes, Novak et al. 2002). However, auditory perception and language skills are difficult to assess accurately in infants (Zimmerman-Phillips, Robbins et al. 2000). Newborn hearing screening programs now in place in 38 states, are expected to identify 30-40 children per day nationally with congenital hearing loss, precipitating the need for assessment and management strategies that utilize early windows of opportunity for interventions (such as a CI) by 12-18 months of age.

Functional magnetic resonance imaging (fMRI), offers a novel tool for evaluation of central auditory processes in infants. fMRI is non-invasive and presents no known biological risks, even for infants.(Zaremba 2003) fMRI may permit differentiation of brain responses corresponding to auditory detection, speech perception and language processing in normal and hearing-impaired infants (Holland, Choo et al. 2004). The ability of fMRI to demonstrate various levels of auditory and language processing in infants and toddlers can provide important data to clinicians that is not available by any other means in prelingual babies. The current proposal is designed to ascertain whether (H2) pre-implant cortical activation patterns revealed by fMRI during infancy will correlate with auditory performance two years after cochlear implantation and whether (H1)fMRI can reveal clinically relevant details about the central auditory system in infancy. Three specific aims are designed to test these hypotheses. We plan to (S1) optimize a silent background, auditory stimulation fMRI method on a clinical 3T MRI system, (S2) acquire fMRI and hearing test data on normal hearing (n=30) and hearing impaired infants (n=60) and (S3) correlate central auditory activation patterns revealed by fMRI in hearing impaired infants at 1 year of age, with outcome measures 2 years after cochlear implantation. Our hope is that successful completion of the proposed study will provide clinicians with a new tool to guide optimal intervention strategies for hearing-impaired infants.

This study is currently taking place on the 3T Siemens MRI system in the CCHMC Radiology department. The SNHL patients included in the study rant in age from 9-15 months and must therefore be sedated for the fMRI scans. Ethical considerations preclude sedation of infants for an MRI research study, and so the subjects included in this project are all referred to MRI for a clinical indication. In the case of the hearing impaired subjects, they are referred to MRI by their Otolaryngologist to examine the temporal bone and the anatomy of the inner ear and cochlea as part of the CI evaluation process. In the case of normal hearing control subjects, these patients are referred by a neurologist or family pediatrician for a brain scan to rule out pathology associated with seizures or other abnormal behavior during infancy. Because these subjects are clinical patients they are scanned on the clinical scanner during sedate imaging slots.

The results of fMRI scans on the Siemens Trio are excellent and we have been able to implement silent background scanning methods on this platform for use with auditory stimulation (Schmithorst and Holland 2004). The combination of the high-quality EPI scans, silent background, event-related scanning, and advance post-processing methods yield robust results from this study in hearing impaired subjects, including infants as shown in Figure 1. However, not all children with severe to profound SNRL receive a CI during infancy. Some children may lose their hearing later in childhood due to infections as described in the project description for Dr. Choo above. Other children may have genetic progressive hearing loss that only requires CI treatment later in life. We are now acquiring preliminary data in older children who are candidates for CI in order to propose an outcome study in such patients, relating pre-implant fMRI to post-implant hearing and language measures. This study need not be done on the hospital scanner. More likely it will be carried out on the research scanner in the IRC. The proposed instrument would provide the same type of high-quality fMRI data we are able to obtain on the clinical 3T Siemens Trio scanner for future studies of central auditory activation in cooperative, awake children with SNHL.

• NIH, RFA: DC-02-004 - Auditory/Perceptual Processing by Infants with Hearing Loss: Issues in Clinical Assessment and Management, 2002 National Institute on Deafness and Other Communication Disorders
• ASHA, Infant hearing bills advance in states, Senate, 1999 American Speech Language Hearing Association.
• Utah, S.U., Universal Newborn Hearing Screening Fact Sheet, 2002 National Center for Hearing Assessment and Management: Utah State University

 

Key references relating to this study - (Holland, Choo et al. 2003; *Zur, Holland et al. 2004; Chiu, Holland et al. 2004; Chiu, V.J. et al. 2004; Holland, Choo et al. 2004; Holland, Choo et al. 2004; Holland, Choo et al. 2004; *Patel, Arjmand et al. 2005; Holland, Choo et al. 2005; Schmithorst, Holland et al. 2005; Holland, Choo et al. 2006; Holland, Choo et al. 2006; Cahill, Mehta et al. 2007; Karunanayaka, Holland et al. 2007; Mecoli, Holland et al. 2007; Mecoli, Karunanayaka et al. 2007; *Patel, Cahill et al. In Press)